Choongmoo Shim - Academia.edu (original) (raw)
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Papers by Choongmoo Shim
International Journal of Materials Science and Applications, 2013
Edge-carboxylated graphite (ECG) was produced by grinding pristine graphite in a planetary ball-m... more Edge-carboxylated graphite (ECG) was produced by grinding pristine graphite in a planetary ball-mill machine. Transmission electron microscope was used to confirm the layers of graphene in ECG. The elemental analyses showed that the oxygen contents are different between ECG samples. The vibrational analysis of single-and five-layered graphene was conducted using finite element method within ANSYS. The vibrational behaviors of cantilevered and fixed graphene with one or five layers were modeled using three-dimensional elastic beams of carbon bonds and point masses. The dynamic analysis was conducted using nonlinear elastic elements within LS-DYNA. The natural frequencies, strain and kinetic energy of the beam elements were calculated considering the van der Waals forces between the carbon atoms in the hexagonal lattice. The natural frequencies, strain and kinetic energy of the graphene sheets were estimated based on the geometrical type and the layered sheets with boundary conditions. In the dynamic analysis, the change in displacement over time appears larger along the x-and y-axes than along the z-axis, and the value of the displacement vector sum appears larger in the five-layer graphene than in the single-layer graphene.
European Journal of Emergency Medicine, 2017
The fatigue life of austenitic stainless steel is significantly reduced in the environment of a p... more The fatigue life of austenitic stainless steel is significantly reduced in the environment of a pressurized water reactor (PWR). One of the methods for evaluating the environmental effect involves the use of the environmental correction factor (Fen) determined from the fatigue lives of the material in air and the PWR environment. It has been reported that the environmental correction factor increases with decreasing strain rate, eventually saturating at a low strain rate. However, the exact behavior of the parameter remains unclear considering evidences of a relationship between environmentally assisted fatigue and stress corrosion cracking. It is therefore of importance to examine the possibility of continuity between environmentally assisted fatigue and stress corrosion cracking at very low strain rates. In the present study, time domain analyses of short fatigue cracks initiated in 316 stainless steel in air and simulated PWR water were used to ascertain the existence of such continuity by investigating the relationship between the environmentally assisted fatigue and stress corrosion cracking. The acquired environmentally assisted fatigue life data were uniquely interpreted, and superposition of the plots of the stress corrosion cracking data obtained by slow-strain-rate tensile tests over the time domain analyses and environmentally assisted fatigue data suggested continuity among the parameters. This was clearly substantiated by further time domain analyses.
Journal of the Korean Institute of Illuminating and Electrical Installation Engineers, Nov 30, 2012
Most of existing wind turbine system is used with geared type; however, this type has lots of pro... more Most of existing wind turbine system is used with geared type; however, this type has lots of problems which are noisy, weight, maintenance and so on. In this paper, wind turbine system with fluid torque converter applied to solve these problems. In case of the proposed wind turbine system, it is possible to transmit torque to adaptable distance. So various sets including generator, inverter and auxiliary motor move from the nacelle to the ground. As a result, Total weight in Nacelle can be decreased. however, the efficiency can be decreased with fluid tourque system.. We also applied auxiliary motor to fluid touque system. So, we also realized rated revolutions and rated output windturbine and could get considerable good data.
International Journal of Materials Science and Applications, 2013
Edge-carboxylated graphite (ECG) was produced by grinding pristine graphite in a planetary ball-m... more Edge-carboxylated graphite (ECG) was produced by grinding pristine graphite in a planetary ball-mill machine. Transmission electron microscope was used to confirm the layers of graphene in ECG. The elemental analyses showed that the oxygen contents are different between ECG samples. The vibrational analysis of single-and five-layered graphene was conducted using finite element method within ANSYS. The vibrational behaviors of cantilevered and fixed graphene with one or five layers were modeled using three-dimensional elastic beams of carbon bonds and point masses. The dynamic analysis was conducted using nonlinear elastic elements within LS-DYNA. The natural frequencies, strain and kinetic energy of the beam elements were calculated considering the van der Waals forces between the carbon atoms in the hexagonal lattice. The natural frequencies, strain and kinetic energy of the graphene sheets were estimated based on the geometrical type and the layered sheets with boundary conditions. In the dynamic analysis, the change in displacement over time appears larger along the x-and y-axes than along the z-axis, and the value of the displacement vector sum appears larger in the five-layer graphene than in the single-layer graphene.
European Journal of Emergency Medicine, 2017
The fatigue life of austenitic stainless steel is significantly reduced in the environment of a p... more The fatigue life of austenitic stainless steel is significantly reduced in the environment of a pressurized water reactor (PWR). One of the methods for evaluating the environmental effect involves the use of the environmental correction factor (Fen) determined from the fatigue lives of the material in air and the PWR environment. It has been reported that the environmental correction factor increases with decreasing strain rate, eventually saturating at a low strain rate. However, the exact behavior of the parameter remains unclear considering evidences of a relationship between environmentally assisted fatigue and stress corrosion cracking. It is therefore of importance to examine the possibility of continuity between environmentally assisted fatigue and stress corrosion cracking at very low strain rates. In the present study, time domain analyses of short fatigue cracks initiated in 316 stainless steel in air and simulated PWR water were used to ascertain the existence of such continuity by investigating the relationship between the environmentally assisted fatigue and stress corrosion cracking. The acquired environmentally assisted fatigue life data were uniquely interpreted, and superposition of the plots of the stress corrosion cracking data obtained by slow-strain-rate tensile tests over the time domain analyses and environmentally assisted fatigue data suggested continuity among the parameters. This was clearly substantiated by further time domain analyses.
Journal of the Korean Institute of Illuminating and Electrical Installation Engineers, Nov 30, 2012
Most of existing wind turbine system is used with geared type; however, this type has lots of pro... more Most of existing wind turbine system is used with geared type; however, this type has lots of problems which are noisy, weight, maintenance and so on. In this paper, wind turbine system with fluid torque converter applied to solve these problems. In case of the proposed wind turbine system, it is possible to transmit torque to adaptable distance. So various sets including generator, inverter and auxiliary motor move from the nacelle to the ground. As a result, Total weight in Nacelle can be decreased. however, the efficiency can be decreased with fluid tourque system.. We also applied auxiliary motor to fluid touque system. So, we also realized rated revolutions and rated output windturbine and could get considerable good data.